1. Field of the Invention
This invention relates to a method of obtaining information of a specified or target area of a living body near its skin surface by the application of a nuclear magnetic resonance (hereinafter referred to as NMR) phenomenon. More particularly, the invention relates to a method of obtaining, with high SN ratio and with ease, information of a specified area of a living body near its skin surface by a measuring instrument directly inserted into the body to approach the specified area or disposed on the skin surface in close proximity thereto.
In concrete terms, the present invention is directed to a measuring method which enables endoscopy of a specified area of a living body or approach thereto from the outside of the body for obtaining high-resolution information on liquids such as intracellular or extracellular sap, various tumors (a benign tumor, a malignant tumor, an inflammatory tissue, etc.) through the medium of an NMR signal of a nuclear magnetic substance (a proton, fluorine, magnesium, phosphorus, sodium, calium or the like) in an organ close to the skin surface of the body (for example, a mammary gland or the thyroid gland), a tubular or cavitary organ (for example, the womb, an intestine, the throat or the like) or an organ incised by a surgical operation or the like. This method is applicable not only to a living body but also to a lifeless target. However, the following description will be made in connection with a living body for convenience of explanation.
2. Description of the Prior Art
For the above mentioned tumor dectection, techniques heretofore employed have included radiometry using X-rays or RI, ultrasonic measurement, and a method of histomorphologically examining a tissue slice sampled by biopsy through a microscope. Further, methods of obtaining information of a specified area of a living target body from the outside thereof by the application of the NMR phenomenon have recently been proposed by the present inventors (U.S. Pat. No. 3,932,805) and R. Damadian (U.S. Pat. No. 3,789,832).
With radiometry, an abnormality of the target area is recognized merely as a "shadow" and the qualitative judgement as to whether the abnormality is a tumor or not, or whether it is benign or malignant, is finally made after a histomorphological examination. The same may be said of the ultrasonic measurement. Further, it is known that the limit of resolution by which an abnormal area in an X-ray or RI image can be discerned is a volume of about 1 ml even by a highly skilled person. Moreover, in the case of sampling the tissue slice from the target body, the sampling process inflicts pain and injury on the target body. Further more, since the sample is taken out from the body, the measurement is carried out under different conditions from those in the body resulting in serious errors and a large amount of time is required for obtaining the results of examination.
On the other hand, the methods of obtaining internal information of a target body from the outside thereof by the application of the NMR phenomenon has a great advantage as a non-invasive method. However, in the case of obtaining information of a specified or target area deep in the body, where the specified area and a signal detector disposed on the outside of the body are spaced more than several centimeters apart from each other, the coupling between them becomes inevitably loose. And, further, the SN ratio of the measuring device is lowered by signal loss due to body tissues existing between the specified area and the signal detector. For enhancement of the SN ratio, it is necessary to employ as strong a magnetic field as possible and it is known that the SN ratio is improved in proportion to substantially the 1.5 power of the field intensity.
Moreover, it is also necessary to use means for erasing pseudo-signals emanating from the region neighboring the specified area, so that the device is inevitably complicated and bulky.